There's no evidence drug use is a barrier to job seeking. And testing can't distinguish between one off, irregular or regular use.

Inside a strip search booth used at music festivals. New research has found strip searches have increased 20 fold in the last 12 years.
Obtained by Redfern Legal Centre from NSW Police Force under the Government Information (Public Access) Act 2009 (NSW)
August 22, 2019

A new study has found more than half of those in drug treatment have cognitive impairments – meaning treatment won't work for them.

Kids teething? Back in 1885, Mrs. Winslow’s Soothing Syrup, containing morphine, was close at hand and earned the nickname the “baby killer.” Concerns about the dangers of readily available medications played a big role in how Canada’s drug laws evolved.
The U.S. National Library of Medicine
August 12, 2018